Depends on your needs, but definately 1
pr. formal, 1
pr. flip flops or other such pool shoe because the decks do get hot, and 1
pr comfortable walking sandals or running shoes for all the walking you'll do. Also 1
pr. water shoes for water-related shore excursions. Flip flops or sandals can double as slippers; you don't want to be walking around barefoot anywhere.
donna